PEALE.] SHOSHONE GEYSER BASIN UNION GEYSER. 255 



maining particulars, the numbers corresponding witli those given on 

 the map. 



Union Geyser (Plate XXX). — This is the most important geyser in the 

 Shoshone Basin. It has three small mounds or craters close together, 

 each of which has an opening or vent. The central one is the princii^al 

 geyser. Professor Bradley says : " We called this the Union Geyser 

 because of its combination of the various forms of geyseric action." 

 The three craters spout simultaneously, although the smallest one is 

 insignificant in its action. 



The central cone is about 3 feet high, and has a circumference of 18 

 feet at the base. The geyserite composing it is beautifully beaded on 

 the outside, the color grading from yellow into gray, with pearly tints. 

 On the top of the cone is a triangular orifice measuring 28 inches on 

 each side. This opens into a globular cavity, which is nearly 5 feet 

 deep and about 3 feet in diameter. It is brownish-yellow inside, and at 

 the bottom is a hole about a foot in diameter. This is the outlet of the 

 tube, and soon narrows and becomes crooked, so that we could not get 

 an idea of its depth. 



The north cone is next in size, and is about a foot in height. It has 

 an irregular orifice measuring 2 J feet by 1 foot. It soon narrows as we 

 go down. This cone is darker in color than the central one. The south 

 cone is small, having a diameter of about 25 inches, and rising only about 

 a foot above the general level. On the summit are two openings several 

 inches in diameter. Between the central and south cones there is a small 

 hole, from which water flows in the period between the eruptions. These 

 cones are situated on a mass of gray and white deposit, which is lami- 

 nated in its structure, and at places appears to be thin, as it is readily 

 broken through. Professor Bradley, as I have said in another place, 

 thinks that the cones of the Union Geyser, together with the Impene- 

 trable Spring, occupy what was once the mouth of an immense geyser. 

 The stream courses leading from the geyser are few, and it is only during 

 the eruptions that there is overflow from the cones. The eruption be- 

 gins with a few preliminary puffs of steam, which precede the spouting 

 of the water only a few seconds. The first spurts of water attain a 

 height of 10 or 15 feet. It rapidly rises to 100 feet or more from the 

 central cone. In the small south cone it lasts a few seconds and is fol- 

 lowed by steam, which escapes gently, while the other cones are in active 

 eruption. In the central cone the water period is about 5 minutes, and 

 in the north cone 10. Steam follows the water in both, escaping with a 

 steady roar that continues several minutes after the water is exhausted 

 in the north cone. This steady volume of steam changes to puffs at 

 intervals of a few seconds, which gradually diminish until the eruption 

 is ended. So gradual is the diminution that it is difficult to say when 

 the eruption ends. The column of water and steam is projected steadily 

 with great force. 



The following transcription of my field-notes will present all the facts 

 concerning the Union noted during our visit to the Shoshone Geyser 

 Basin: 



August 14. — We reached the Shoshone Geyser Basin early in the 

 afternoon and camped near the Union Geyser. The craters of the gey- 

 ser are full, and in the central one it spurts at intervals to the height of 

 a foot or more. 



August 15. — At G.45 p. m. an eruption began, all the cones sending up 

 water, that in the smallest lasting but a short time. In the middle cone it 

 lasted about 5 minutes. At 6.56 p. m. the water in the north cone be- 

 came exhausted and the steam cajne out in volumes with a steady roar, 



